Fe-cr-ni alloys



United States Fe-Cr-Ni ALLOYS No Drawing. Application August 24, 1954, Serial No. 451,967

7 Claims. (Cl. 7 -128) This invention relates to alloys containing iron, nickel and chromium. The use of such alloys precipitation hardened by titanium :for high temperature service is known and various proposals for the manufacture of such precipitation hardened alloys have been made, see for example, U. S. Patent No. 2,519,406.

In practice it is generally accepted that these alloys precipitation hardened by titanium require to have an exceedingly low carbon content, i. e. less than 0.05%, otherwise the desirable nickel-titanium precipitation hardening complexes are suppressed at the expense of relatively inert titanium carbide.

The basis of the present invention is the use of small percentages of niobium and/or tantalum in iron-nickelchromium alloys precipitation hardened by titanium. One advantage of this is that, owing to the strong carbidef-orming powers of niobium and/ or tantalum, somewhat higher carbon contents may be used where necessary (for example, to facilitate melting) while maintaining satisfactory mechanical and creep strengths.

According to the present invention, alloys consist of the following constituents in the amounts by weight as stated in the following ranges:

Percent Carbon up to 0.15 Nickel 20-26 Chromium 11-15 Cobalt 0-2 Niobium and/ or Tantalum 0.2-0.8 Molybdenum 2.3-3.3 Titanium 1.5-2.5 Iron and impurities Balance The usual deoxidisers, manganese, silicon, calcium, aluminum, etc. may be present but the total amount should not normally exceed 3%.

A more restricted range for carbon is 0.08%-0.15% and still further restricted range is 0.06%-0.13% Alloys according to this invention may be solution treated in the temperature range 1,000 C. to 1,250 C. and age-hardened in the temperature range 600 C. to 700 C.

An example of an alloy which is designated by the reference L. 1107 according to this invention is:

zsaassa Patented Aug. 2Q, 1957 Such an alloy when solution treated at 1100 C., and suitably age-hardened in the temperature range 650-750 C. has thefo llowing properties:

0.1% proof stress -.tons/ sq. in 44 Maximum stress do 69 Elongation percent 18 Reduction of areas do 25 Wex 603 L. 1365 L. 1366 13.1 12. 8 13.6 0.88 0. 52 2. 60 2. 36 2.30 0.35 0. 41 0.33 0. 49 0. 49 0.46 1. 52 1. 96 1. 84 Balance Balance Balance These alloys, after being hardened substantially as in the case of alloy L. 1107,

solution treated and age- Stress-rupture tests have been carried out at 600 C. and 700 C. on these three alloys with the following results:

Rupture Time Rupture Time Alloy at 28 Tons/sq. at 16 Tons/sq.

in., 600 0., in., 700 0., hours hours Wex 603 167 72 L. 13 115 74 L. 1366 138 101 It will be seen from these results that in the presence of niobium and tantalum the high proof stress at room temperature and the high maximum stress is not diminished by the presence of carbon up to 0.15%. The same remarks apply to the rupture stress at 6 00 and 700 C.

It may be observed that the superior creep-rupture properties of the alloy L. 1107 are attributed to the higher titanium content of the alloy. Such a high titanium con tent is suitable where high creep strength is of importance but contents of the order of 1.8%-2% are preferred for easy manipulation where the room temperature proof strength is the more important property being sought. It will be noted that the figure of 44 tons per square inch for the 0.1% proof stress of alloy L. 1107 was no better than the corresponding values for alloys L. 1365 and L. 1366, i. e. alloys within a titanium range of 1.8-2%.

Percent Carbon"--- 0.05-0.15 Nickel 20-.26 Chromium 11-15 Cobalt 0-2 At least one metal of the groupconsisting of niobium and tantalum 0.2-0.8

Molybdenum 2.3-3.3 Titanium 1.5-2.5 Iron and impurities Balance 2. Alloys as claimed in claim 1 in which the range of carbon is 0.08-0.15%.

3. Alloys as claimed in claim 1, in which the'range of carbon is 0.060.13%.

A 4 4. Alloys as claimed in claim 1, in which the range of titanium is 1.8-2%.

5. Alloys as claimed in claim 1, in which the usual deoxidisers, manganese, silicon, calcium, aluminum are 5 present in usual proportions.

6. Alloys as claimed in claim 5, in which the elements referred to are present in a total amount not exceeding 3 7. Alloys according to claim 1, which have been solution treated in the temperature range 1,000 C. to 1,250

10 C. and age-hardened in the temperature range 600 C. to

References Cited in the file of this patent UNITED STATES PATENTS 16 2,519,406 Scott Aug. 22, 1950 2,758,025 Clarke Aug. 7, 1956 FOREIGN PATENTS 134,433 Australia Sept. 26, 1949 

1. ALLOYS CONSISTING OF THE FOLLOWING CONSTITUENTS IN THE AMOUNTS BY WEIGHT AS STATED IN THE FOLLOWING RANGES: 